Since the 3D printing industry evolves every month, does someone know if it's now interesting to print cartdrige/shell ?
Are we still talking about easy to break 3D printed cart ? I read recently about plastic-w-carbon and resin, so I expected the 3D printed objects are now more and more difficult to break, no ?
if yes, what about the cost ? did it finally drop down ?

note: i'm not talking about Genny cart of course, but for others sys which haven't the chance to be massively china-cloned

For small scale stuff it does make sense to 3D print things. Mechanically they can be good but you got to design things appropriately. If you need hundreds of cartridges then 3D printing is gonna be on the verge of not cheap plus it also takes a long time to make those carts. For thousands you can definitely forget 3D printing.

My FDM printer prints ABS plastic just fine, which is the same plastic used to make most cartridges.
I havent yet seen any weaknesses by delamination, and i reckon the parts can be stronger than some injection molded ones lenghtwise.
Also, Printing artifacts and layer lines are easy to remove from ABS with acetone.
I also have printed some nylon, which is a little bit harder to get right. But a test M10 bolt&nut i made from nylon proved to bee too tought to break by hand so theres that.
I could test print a MD cart tomorrow with black ABS if you wish?

For most people, tinkercad is enough. For more flexible features Autodesk's "Fusion" is free for people that generate less than 100k of yearly revenue from their product. However if you have money to burn, the best solution would "Solidworks" by Dassault systèmes.

There is also Blender, which is free, and you can get a few CAD-tools for it.
I recommend that you take a look at Fusion, and if you're interested in more organic/artistic 3d designs, then take a look at blender.

Basically, Any software that can export the model in: STL, OBJ, FBX is compatible with most slicers and toolpath generators.

If you need help with any 3D modelling/CAD-CAM software then feel free to contact me.